Field
Embodiments disclosed herein generally relate to a showerhead for forming films on substrates, such as semiconductor substrate and, more specifically, a dual channel showerhead for film stack formation.
Description of the Related Art
Semiconductor processing involves a number of different chemical and physical processes enabling minute integrated circuits to be created on a substrate. Layers of materials which make up the integrated circuit are created by chemical vapor deposition, physical vapor deposition, epitaxial growth, and the like. Some of the layers of material are patterned using photoresist masks and wet or dry etching techniques. The substrate utilized to form integrated circuits may be silicon, gallium arsenide, indium phosphide, glass, or other appropriate material.
In the manufacture of integrated circuits, plasma processes are often used for deposition of various material layers on substrates. Plasma processing offers many advantages over thermal processing. For example, plasma enhanced chemical vapor deposition (PECVD) allows deposition processes to be performed at lower temperatures and at higher deposition rates than achievable in analogous thermal processes. Thus, PECVD is advantageous for integrated circuit fabrication with stringent thermal budgets, such as for very large scale or ultra-large scale integrated circuit (VLSI or ULSI) device fabrication.
Precursor gases for forming film stacks such as oxide-nitride-oxide (ONO) stacks and oxide-polysilicon-oxide (OPO) stacks are delivered to the substrate through a showerhead. A plasma of the gases is formed in or near the showerhead as the gases exit openings of the showerhead and reactive species are deposited on the substrate to form the various films.
However, the precursor gases are typically delivered through the same openings in the showerhead (e.g., a single channel showerhead). This type of showerhead is limited in terms of plasma density, which limits deposition rate and throughput. Further, oxide precursors and nitride precursors have different flow sensitivities as well as different sensitivities to electromagnetic energy that is utilized to form the plasma. Additionally, the conventional showerheads may leave a visual imprint on a substrate that matches the pattern of openings in the showerhead, which is undesirable.
Therefore, what is needed is a showerhead that includes discrete channels for uniform delivery of oxide and nitride precursors.